Synthesis of Imidazolium Based Ionic Liquids and its Application as Medium in Cyclization Reaction of Diketone

Abstract

Ionic liquids (ILs) are organic salts that have a liquid phase under 100°C. Due to its ionic nature, it has affinity with water as well as organic compounds that make it potential to be developed as solvents with tuneable property. One class of material that possess this property is imidazolium compound which serves as organic cation. Variations of substituents (alkyl or aryl groups) in the parent cation provide several compounds that can be used as medium in various reactions. In this research, the synthesis of several imidazolium based ionic liquids had been performed utilizing Microwave Assisted Organic Synthesis (MAOS) method namely: butyl-methyl imidazolium chloride (BMIM-Cl), Decyl-methyl imidazolium bromide (DMIM-Br), Dodecyl-methyl imidazolium bromide (DDMIM-Br). The ILs were subsequently used as medium in cyclization reactions of diketone to provide an alternative route to flavanon. The structure of the synthesized ILs and the cyclization product were characterized by FT-IR and 1H-NMR spectroscopy. The yield of the synthesized ILs were moderate (24-87%) while the yield of cyclization reactions was high (99%). The formation of the cyclization product, was clearly indicated by the 1H-NMR spectrum with the peaks that appear at 6.81 ppm as singlet which corresponded to the proton at the pyranone ring.